1. Field of the Invention
The present invention relates to a chain guide including a guide shoe that slidably guides a traveling chain and a guide body that supports the guide shoe along the direction of travel of the chain.
2. Description of the Related Art
Conventionally, a chain guide including a guide shoe that slidably guides a traveling chain is commonly used in order to stabilize the chain traveling between sprockets and properly maintain tension.
For example, as shown in FIG. 5, there is known a timing system of an engine that causes a transmission chain CH such as a roller chain or the like endlessly wound between sprockets S1 and S2 provided at a crankshaft and a camshaft in an engine room E to travel in which the timing chain CH is endlessly wound between the driving sprocket S1 attached to the crankshaft in the engine room E and a pair of the driven sprockets S2 attached to the camshaft, and the timing chain CH is guided by a pivoting chain guide (pivoting guide) 500 and a chain guide (fixed guide) 600.
In this known timing system, the fixed guide 600 is fixed in the engine room E with two mounting shafts Q, while the pivoting guide 500 is mounted in the engine room E so as to be pivotable about a pivot P in the plane of winding of the timing chain CH.
A chain tensioner T presses the pivoting guide 500 to thereby properly maintain the tension of the timing chain CH and suppress vibrations.
As shown in FIGS. 2B, 6, and 7, the known chain guide (pivoting guide) 500 used in such a timing system includes a guide shoe 510 and a guide body 520, and the guide body 520 has a pivoting boss portion 523 pivotably supported via a support wall portion 521 that extends to the side opposite to a chain travel surface 511, and a pressed portion 524 that is pressed to the side of the chain by the tensioner T.
In addition, in the support wall portion 521, a reinforcing rib 522 in an appropriate shape is provided at an appropriate interval in an appropriate direction, and the rigidity of the guide body 520 is thereby enhanced.
At both sides of the chain travel surface 511 of the guide shoe 510, lips 512 that protrude to the side of the chain are provided in order to prevent the detachment of the chain in a width direction.
The chain travel surface of the guide shoe 510 slides relative to the chain and the temperature of the chain travel surface is increased to a high temperature, and hence it is necessary to have a predetermined distance between the guide shoe 510 and the pivoting boss portion 523 in order to prevent the deformation of the pivoting boss portion 523 by heat, the enlargement of a gap with the pivot P, and the generation of vibrations or the like.
In addition, a large force is applied to the pressed portion 524 that is pressed to the side of the chain by the chain tensioner T, and hence the pressed portion 524 is configured such that the rigidity thereof is enhanced by having a long distance to the guide shoe 510 (see Japanese Patent Application Laid-open No. 2001-153199).
The known chain guide (fixed guide) 600 has the structure similar to that of the chain guide (pivoting guide) 500 except that two fixed boss portions to be fixed to the two mounting shafts Q are provided instead of the pivoting boss portion 523 and the pressed portion 524 of the above-described chain guide 500, and has almost all of its structure on the side opposite to the chain travel surface (in the example of FIG. 5, on the outer peripheral side of the timing chain CH in the engine room E).
In the known chain guide described above, in order to secure the rigidity and durability of the chain guide, although it is necessary to increase the size of the guide body to improve the rigidity and durability thereof, since the known chain guide has almost all of the structure on the side opposite to the chain travel surface, in a case where the timing chain CH is guided from the outer peripheral side of the timing chain CH in the engine room E as shown in the example of FIG. 5, there has been a problem that it is not possible to enlarge the guide body to the inner peripheral side and a space needs to be secured on the outer peripheral side, which makes it difficult to design the engine room E compactly.
In addition, since the lips protruding to the side of the chain are provided at both sides of the guide shoe in the width direction for preventing the detachment of the chain in the width direction, it is necessary to increase the size of the guide shoe. However, since it is necessary to use an expensive material optimum for sliding for the guide shoe, there has been a problem that its cost is increased.
With regard to this point, for example, like Japanese Patent Application Laid-open No. 2009-85412, a technique that can reduce the size of the guide shoe by separately providing a guide wall on the outside of the guide shoe is known. However, there has been a problem that the number of components is increased and costs in assembly and maintenance are increased.